Line Chromatic Confocal Measurement System With Linear Variable Filter

In recent years,with the development of science and technology,there have been higher requirements for the accuracy and speed of three-dimensional measurement technology in industries such as machinery manufacturing,optical processing,chip manufacturing,semiconductor manufacturing.Line chromatic confocal technology can obtain the height information within line field of view in real time and realize continuous and high-speed three-dimensional topography measurement.In this thesis,a line chromatic confocal measurement system with linear variable filter(LVF)is proposed,which has the advantages of simple structure,low cost and large measuring range.Firstly,the background of the research problem is expounded,and the concept of chromatic confocal and the development and research status of line chromatic confocal technology are introduced.According to the principle of line chromatic confocal,a line chromatic confocal method using LVF is proposed,and its system composition and working principle are given.Based on the Scheimpflug imaging law between inclined conjugate planes,the relationship between the performance parameters such as measurement resolution,measurement range,allowable inclination angle of the measured plane,working distance and the structural parameters of the optical system is analyzed,and the numerical aperture,magnification and the angle between the optical axis and the linear gradient filter and the imaging focal plane of the optical system to be designed are determined.A dual-axis chromatic confocal imaging optical system with a magnification of-1,a numerical aperture of 0.2 and a working band of 450-600nm is designed.The axial and lateral measurement ranges of the surface to be measured are 5mm and 12 mm respectively,and the measurement resolution is 3.6 μm.Finally,a two-axis chromatic confocal principle experimental device based on the existing LVF is built,and the feasibility and characteristics of the LVF as a chromatic element of the linear chromatic confocal system are verified by experiments.Through data processing methods such as calibration with standard gauge block and peak position extraction with weighted centroid method,the axial measurement range of the device can be greater than 5 mm,the standard deviation of repeatability test is 1.4 μm,and the average absolute error is 1.6 μm.This thesis lays a technical foundation for the further development of line chromatic confocal measurement system with large range,compactness,high linearity and small distortion.